The objectives of this research project are to study the metabolism of lysine and its neurochemically active metabolites in the rat and monkey brain, to study the kinetics of the blood-brain barrier transport of lysine metabolites, to study the effects of nutrition on lysine metabolism and lysine metabolite levels in the brain, and to study the neurochemistry of lysine metabolites and their relationship to other neurotransmitters. Further detail of the brain pipecolic acid pathway which was demonstrated in our previous study, will be studied by the use of both the in vivo (intraventricular injection) and in vitro techniques. Various coenzymes, cofactors and stabilizers will be used in order to establish a working in vitro system for lysine metabolism. Isotope, chromatographic and mass spectrometric techniques will be applied in the pathway study in order to enhance the sensitivity of analysis. A tissue-sampling, single-injection technique will be used for the blood-brain barrier transport study. Kinetic analysis of the transport mechanism will be conducted for this study. The effects of dietary lysine levels and vitamin deficiency on the brain lysine metabolism will be examined by the intraventricular injection technique and analysis of enzymes related to lysine metabolism. The resultant changes of lysine metabolite levels in the rat brain as a result of this treatment will also be analyzed by the use of high-pressure liquid chromatography and mass spectrometry. The neurochemical roles of lysine metabolites as neurotransmitters or transmitter antagonist will be studied by the techniques of discontinuois density gradient, metal ion-dependent high-affinity uptake and continuous superfusion of brain synaptosomes. Kinetic study of the uptake of lysine metabolites by synaptosomes will be attempted. It is hoped that the knowledge obtained from this research work will help understand the neurochemistry of lysine and its metabolites in the human being.